1. Field of the Invention
This invention relates to a positioning apparatus for the magnetic head of a magnetic disk drive apparatus.
2. Description of the Prior Art
Recently, there has been developed a magnetic disk drive apparatus using a spring to return a carriage, on which a magnetic head is mounted, to a fixed position whenever a power source is cut off. In order to position the head over a desired track, it is necessary to overcome the biasing force of the spring on the carriage. The prior art magnetic disk drive apparatus compensates for the biasing effects of the spring by using a controller which includes a low pass integrator to position and keep the magnetic head positioned over the desired track. If the time constant of the low pass integrator is too small, however, the closed loop of the controller might oscillate and the time constant therefore must be sufficiently large. If the time constant is too large, however, unfortunately the transient time in changing from speed control of the magnetic head to position control of the magnetic head to keep it on track becomes too long.